This invention relates to a process for determining whether microorganisms, that is, airborne microorganisms such as viruses, spores, bacterial cells, yeast cells, and the like, are escaping from equipment or building installations designed to confine them, and if so, for detecting the general location of the leak and its magnitude.
Systems for distributing air such as air conditioning and forced hot air heating systems potentially provide an airstream which can carry unwanted microorganisms and other particles into living space, areas devoted to health care, clean rooms used to produce solid state devices or pure microbiological cultures, and other areas. Biological containment cabinets and glove boxes are designed to provide a barrier, e.g., and air curtain, between a work space within the hood and the ambient environment. Improper installation, maintenance, design, or construction of such devices may lead to improper functioning of an air curtain, seal, filter, or the like, and may result in contamination of the environment or workspace with foreign, live microorganisms.
While the injection into such a system of a smoke, fog or other visually detectable fluid such as a colored gas may be used to detect air leaks, this approach cannot detect the escape of extremely small numbers of airborne microorganisms with the sensitivity required in the more demanding problems of biological containment. For example, the escape of even a single viable bacterial spore or other viable microorganism potentially can destroy a costly and tedious genetic engineering effort or lead to a health risk. Consequently, the National Sanitation Foundation (NSF) requires efficacy testing of prototype biological containment hoods.
The NSF currently has accepted a "Bacterial Aerosol Tracer" test as a minimal efficacy test for biological containment hoods. To conduct the test, a technician sprays a fog of viable microorganisms, typically bacterial spores, into the containment hood while the hood is in operation. Typically 1.times.108 to 8.times.108 spores are introduced over a five minute period. Particle traps are situated on the outside of the air curtains and at other locations where there is a possibility of particle escape. The technician subsequently adds the contents of the traps to a medium designed to promote growth of the test microorganism, and after a suitable incubation period, inspects the culture vessels for colonies of bacteria. Because each spore can reproduce repeatedly to form a detectable bacterial colony, this test enables detection of the escape of even a single spore. Generally, the detection of 10 or more microorganisms is indicative that the hood is not functioning properly.
While the foregoing procedure works well, it cannot be used at the site of installation of a containment hood because of the unacceptable risk of contaminating the site with foreign microorganisms. Its use in testing air moving systems associated with clean rooms and operating rooms is similarly limited. For this reason, postinstallation testing of such equipment and facilities is generally limited to determining whether filters, duct systems, air flows and air movers are operating according to specifications, but cannot assure that the equipment as a whole is operating as intended.
There is accordingly a need for a simple, sensitive airborne particle detection technique which obviates the risk of contamination by live microorganisms and can be conducted readily at the site of installation of the equipment or installation being tested. It is an object of the invention to provide a family of such tests. Another object is to provide test kits for use in detecting leaks of airborne microorganism and other particles in equipment including gas movement apparatus after installation of the apparatus and at intervals thereafter for maintenance purposes. Still another object is to provide tests of the type described which may be correlated with the accepted Bacterial Aerosol Tracer test.
These and other objects of the invention will be apparent from the description, drawing, and claims which follow.